Warnings ramped up over rivers' toxic algae

Toxic algae risks have worsened for river users and their pets in Masterton and Carterton, according to health and council watchdogs.

Warning signs have been posted at the Waipoua River at Colombo Rd, where there is a high risk level, and at the Ruamahanga River at Kokotau, where the risk is moderate, after increasing levels of toxic algae (cyanobacteria) were detected.

A health warning also had been issued for Henley Lake in Masterton.

Summer Greenfield, senior environmental scientist with Greater Wellington Regional Council, said toxic algae can be abundant in many New Zealand waterways during the summer months. "The warm weather in Wairarapa is a key factor behind the increase. The risk to river users and dogs is likely to remain until there's significant rainfall to flush the algae away."

Toxic algae form brown or black clumps on river beds and can kill livestock and dogs. Contact with toxic algae can cause vomiting, diarrhoea, skin irritations and other allergy-type symptoms in humans.

The regional council, the district councils in Masterton and Carterton and Greater Wellington public health officers urge river users to protect themselves and their dogs from the algae.

Rivers users with pets or people drawing water from the river for stock or human consumption should avoid exposed or easily accessible algal mats both on the riverbanks or floating on the surface of shallow areas and rocks in the rivers.

Avoid swimming near the algae. Put your dog on a lead and move away from the river's edge. Take your dog to a vet immediately if you think it has eaten toxic algae and contact your doctor if you believe you are having a reaction to toxic algae.

For up-to-date warnings on the toxic algae risk at popular Wairarapa rivers, and for an image gallery identifying toxic algae, go online to www.govt.nz/toxic-algae.